1. Field of the Invention
The present invention relates to gyroscopes and more particularly to a permanent magnet, two degree of freedom gyroscope which utilizes sensors and a z-axis torquer for closing the rotor positioning servo loop around the two degree of freedom gyroscope.
2. Description of the Prior Art
It is known in the art to use permanent magnet motors for driving inertial gyroscope sensing instruments. U.S. Pat. No. 4,818,922 describes a prior art permanent magnet motor drive for a gyro rotor. Permanent magnet motors are utilized in inertial gyroscope sensing instruments where optimum efficiency, rate stability and low run up time are required. The drive motors include a two phase stator, permanent magnet rotor and suitable drive circuitry to start, run up and maintain synchronous speed. The rotor is supported by a hydrodynamic bearing wherein the spinning rotor supplies the pressurized fluid for the bearing.
In conventional two degree of freedom gyros, two separate control paths are utilized using an angle sensor on each axis and a torque transducer acting about each axis. The conventional cartesian or rectangular coordinate means of closing the X-Y loops in a two degree of freedom instrument are described in U.S. Pat. No. 4,862,050. In conventional two degree of freedom gyro loop implementations two separate control paths are utilized using an angle sensor on each axis and a torque transducer acting about each axis. The separate angular sensors are used for sensing tilt about stationary X and Y axes and two separate torquers are used for implementing two stationary servo loops to urge the actual rotor spin axis to the nominal or null spin axis. The output signals from the two sensors serve as inputs to the torquer servo control electronics. The servo control electronics extracts and processes the angular displacement information and provides the drive currents to the two torquers to obtain two axes control.
The present invention eliminates the use of two torquers and two sensors and utilizes a single sensor and a single torquer to obtain two axis control of the gyro rotor.